The Condensation of Gasoline from Natural Gas

Bulletin 88 Petroleum Technology 20

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Page.
Introduction 3
General statement regarding wastes of natural gas 3
Occurrence of gas and oil 4
Factors affecting flow of gas and oil in different sections of the same field or in neighboring wells 6
Effect of drilling neighboring wells 8
Effect of formation of waxy sediment 8
History of the making of gasoline from natural gas 9
Two successful plants in 1904 9
Early methods 9
Later improvements 10
Patents issued 10
Production of gasoline from natural gas in the eastern part of the United States. 11
The gasoline industry in West Virginia 11
The industry in Pennsylvania 12
The industry in California 13
Production in 1912 13
Noteworthy interest in the industry 14
Marketing the product 14
Distribution of plants 15
Methods employed 15
Details of equipment 16
Importance of water supply 16
Specific gravity and price of product 16
The industry in the Mid-Continent field 17
Details of production 17
Quantity and value of condensate 17
Future of the industry in Oklahoma 18
Development of industry in foreign countries 19
Total gasoline production in the United States 19
Production in 1911 and 1912 19
Production in 1913 19
Chemistry of natural gas 20
Natural-gas analyses made by the bureau 20
Notes 23
Comments on the analyses 24
Method of analysis used 24
Properties of the paraffin hydrocarbons 25
Occurrence of gasoline in casing-head gas 26
Relation of character of oils in the sand 27
Effect of pressure and temperature on gases in the strata 28
Testing natural gases for gasoline content 30
Classification of kinds of natural gas 30
"Dry" natural gas 31
"Wet" natural gas 31
III

Page.

PLATE I. A, Exterior view of gasoline plant at Sistersville, W. Va.; B, Gasoline plant being erected near Kiefer, Glenn pool, Okla.; C, Small gasoline plant at Reno, W. Va 56
II. A, Cooling coils and accumulator tanks of gasoline plant; B, Gasoline plant accumulator tanks 56
III. A, Gas engine and belt-driven compressor in gasoline plant; B, Double-stage belt-driven compressor 58
IV. A, Results of an explosion in a gasoline plant; B, Part of stillhouse of a plant for condensing gasoline by refrigeration; C, General view of plant for condensing gasoline by refrigeration 58
V. A, Oil well from which casing-head gas is drawn for near-by plant; B, Exterior view of gasoline plant, showing tanks and derricks 60
VI. A, Interior of gasoline plant equipped with six 50-horsepower, direct-connected compressors 60
Figure 1. Apparatus for determining the gasoline content of natural gas 33
2. Orsat apparatus for determining carbon dioxide and oxygen in natural gas 35
3. Apparatus for determining specific gravity of gas 36
4. U tube for measuring flow of gas 37
5. Pitot tube with at~chment for measuring static pressures 40
6. Weights of 1 cubic foot of air at various temperatures, pressure being constant at 30 inches of mercury 43

Figure 7. Weights of water at different temperatures 44
Figure 8. Diagram illustrating physical changes that take place in the production of gasoline from natural gas 54
Figure 9. Compression type of plant for making gasoline from natural gas. Plan 55
Figure 10. Compression type of plant for making gasoline from natural gas. Elevation 56
Figure 11. Evaporation losses of natural-gas condensation 86
Figure 12. Evaporation losses when two natural-gas condensates were mixed with naphtha in different proportions 87
Figure 13. Evaporation losses from a condensate with a specific gravity of 93 B., and from the same condensate mixed with kerosene and with
naphtha 88
Figure 14. Evaporation losses from a condensate with a specific gravity of 95 B., and from the same condensate mixed with kerosene and with naphtha 89
Figure 15. Vapor-pressure curves of natural-gas condensate under different conditions 90
Figure 16. Vapor-pressure curves of two condensates 90
Figure 17. Vapor-pressure curves of a freshly drawn condensate and of a blend of 50 per cent of the condensate and 50 per cent of refinery naphtha 91
Figure 18. Vapor pressures of different mixtures of a condensate with naphtha and with kerosene 92

TABLES.

Page.
TABLE 1. Details of production of gasoline from natural gas in tile Mid-Continent field in June, 1913 17
TABLE 2. Results of analysis of samples of natural gas 21
TABLE 3. Table to be used in testing gas wells with Pitot tube 39
TABLE 4. Results of laboratory arid field tests of 16 different wells on the same lease 47
TABLE 5. Results of laboratory tests of samples of gas from different gasoline plants 61
TABLE 6. Evaporation losses of natural-gas condensate from plant A when allowed to stand exposed to the air 77
TABLE 7. Evaporation losses of natural-gas condensate from plants B and C when allowed to stand exposed to the air 77
TABLE 8. Evaporation losses of natural-gas condensate from plant, A mixed with refinery naphtha 77
TABLE 9. Evaporation losses of different mixtures of natural-gas condensates and refinery naphtha 78
TABLE 10. Evaporation losses of condensates from the same plant, but of different specific gravities 81
TABLE 11. Evaporation losses of mixtures of natural-gas condensates and refinery naphthas 81
TABL E 12. Comparative evaporation losses of blends prepared by mixing different proportions of condensate and naphtha and of condensate alone. 84

THE CONDENSATION OF GASOLINE FROM NATURAL GAS.

By GEORGE A. BURRELL, FRANK M. SEIBERT, and G. G. OBERFELL.

INTRODUCTION.

The Bureau of Mines is conducting a series of investigations with the common aim of minimizing the losses that occur in the mining and treatment of mineral substances. The results of the investigations are being published in reports of the bureau. This report treats of a method of preventing some of the waste of the natural gas incidental to oil mining. This method, the condensation of gasoline from natural gas, offers to the oil operator and others a profitable means of utilizing some of the oil-well gas now being wasted. The most desired constituent of crude oil is obtained, the production of oil is not hindered, and the gas, after the extraction of gasoline, can be returned to the leased area to drive pumps or into pipe lines for uses to which natural gas is ordinarily put, usually with its fuel value lessened only in slight degree.

Publications already issued(a) briefly discuss the subject. In this report the work is treated in greater detail, and the results of many additional tests are shown.

GENERAL STATEMENT REGARDING WASTES OF NATURAL GAS.

Arnold and Clapp (b) classify as follows the various ways in which natural gas is wasted:

(a) In drilling and casing wells.
(b) From high-pressure wells.
(c) In oil production.
(d) Through lack of proper care of wells.
(e) In transportation.
(f) In utilization.
(g) Through improper plugging of wells.

This report concerns itself with method c, the waste incident to oil production.

A. B. Macbeth, chairman of a committee on conservation appointed by the Natural-Gas Association of America, presented at the annual

(a) Allen, I. C., and Burrell, G. A., Liquefied products from natural gas; their properties and uses: Technical Paper 10, Bureau of Mines, 1912, 23 pp.; Burrell, G. A., and Seibert, F. M., The sampling and examination of mine gases and natural gas: Bull. 42, Bureau of Mines, 1913, 116 pp.
(b) Arnold, Ralph, and Clapp, F. G., Wastes in the production and utilization of natural gas and means for their prevention: Technical Paper 38, Bureau of Mines, 1913, 29 pp.

3

Where oil and gas are found in the same field, it is the general practice to blow off the gas. In some fields where the rock pressure is low and the production of both oil and gas is small, some operators are able to produce and market both oil and gas from the same sand. In large operations no practicable way is found of obtaining the oil without wasting the gas, and this is the principal cause of the depletion of many gas fields, and is responsible for a greater waste of gas than all other causes put together. It is natural for the owners of a well to want to produce and sell the well's full production, whether oil or gas, in the shortest possible time, but it is impossible to market gas in the way oil is marketed, for gas can not be stored like oil. The committee saw no way of saving the gas from these wells without seriously affecting the oil production.

Arnold and Clapp (b), Arnold and Garfins (c),and Blatchley (d) also discuss various means of preventing the waste of natural gas. They briefly mention the production of gasoline from gas. Arnold and Clapp (e) state that at some wells the value of the recoverable gasoline in the gas is worth as much as 20 per cent of the oil produced, and that it is not extravagant to estimate the loss in gasoline, at 10 per cent of the oil produced, or, up to 1912, a clear loss of $4,000,000.

OCCURRENCE OF GAS AND OIL.

Gas may be found in a sand and separate from oil. It may be found in more than one sand separate from the oil, or the gas sand may be just above and in contact with the oil sand. A given sand may produce oil and gas in one place and in another part of a territory gas only.

Gas may come from the same sand as the oil itself. It is this manner of occurrence of gas and oil that the authors desire to emphasize, for under these conditions the gas is frequently mixed with enough of tho gasoline constituteuts of the oil to warrant the erection of a plant for the purpose of condensing the gasoline.

(a) Report of committee on the conservation of natural gas: Proc. eighth ann. meet. Natural-Gas Assn. Am., vol. 6, 1913, p. 240.
(b) Arnold, Ralph, and Clapp, F. G., Wastes in the production and utilization of natural gas, and means for their prevention: Technical Paper 38, Bureau of Mines, 1913, 29 pp.
(c) Arnold, Ralph, and Garfins, V. R., The prevention of waste of oil and gas from flowing wells in California, with a discussion of special methods used by J. A. Pollard: Technical Paper 42, Bureau of Mines, 1913, 15 pp., 2 pls., 4 figs.
(d) Blatchley, R. S., Waste of oil and gas in the Mid-Continent fields: Technical Paper 45, Bureau of Mines, 1914, 57 pp.
(e) Arnold, Ralph, and Clapp, F. G., op. cit., p. 11.

OCCURRENCE OF GAS AND OIL 5

The gas usually finds its way to the atmosphere through the space between the casing of the well and the tubing inserted for the removal of the oil. This gas is the so-called "casing-head gas." At the beginning of an oil flow when the flow is natural, a large quantity of gas escapes to the air through the same tubing as the oil. Where the gas finds its exit to the atmosphere apart from the oil at the casing head it is a simple matter to make pipe connections between the casing head and any desired point where the gas is to be utilized. This is frequently done when the supply of casing-head gas is sufficient to warrant its utilization, but frequently, when the supply exceeds the small demands of the lease, the excess is wasted.

When a well is first drilled, the quantity of gas escaping with the oil from the tubing is frequently enormous, being 10,000,000 to 15,000,000 feet or more at times. This gas is wasted. The flow in time diminishes.

When gas comes with the oil in the flow pipe, the two are often separated by means of a gas trap. The oil, entering the top of a drum, settles to the bottom and is withdrawn, and the gas flows off at the top. Many of the plants in California utilize gas that flows with the oil for condensing gasoline. One gasoline plant in the Cushing field, Okla., also uses trap gas. A new type of trap for saving gas from gushers and separating the gasoline is described at the end of this report (p. 99).

Oil wells that have passed the flowing stage and are being pumped may still continue to give off much gas at the casing head. The quantity may vary from little or nothing at some wells to 500,000 cubic feet or more at others. When enough of the gas is available, it is used for pumping on the lease, the excess being wasted. A steam pumping engine of 50 horsepower requires about 25,000 cubic feet of gas for 10 hours' operation. From 12 to 15 cubic feet of natural gas is needed per horsepower-hour for gas engines that are used on leases for pumping oil wells. If there is not enough of the gas available for working pumps, it is all allowed to go to waste, or perhaps some is used for heating and lighting a few scattered houses on the lease.

The efficient utilization of the wasting casing-head gas ordinarily is a difficult problem. The many miles of pipe that would have to be laid to transport it from a field would usually be an unwarranted expense. However, some towns, among which may be mentioned Warren, Pa., and Sisterville, W. Va., are lighted and heated largely with casing-head gas.

In general, however, the oil man considers casing-head gas as waste gas and its escape necessary in oil-well operations, to permit the maximum flow of oil into the well from the surrounding strata.

6 CONDENSATION OF GASOLINE FROM NATURAL GAS.

Huntley (a) discusses the free escape of gas as one of the causes of the decline of oil fields, the action being somewhat as follows:

(1) Excessive refrigeration duo to the free expansion of large quantities of gas forms waxy sediments in the productive stratum and in the tubing of the well. This sediment obstructs the passage of the oil from the sand.

(2) The gas in the immediate vicinity of the well dissipates itself in the initial flow, and the oil production therefore falls' off, owing to a lessening of the expulsive force.

The rapid exhaustion of the gas in a certain part of the field may remove the only influence retarding the encroachment of water, which may, by a flanking movement, cut off a large section of the producing area; or water may exist in the lower part of the oil sand, being held in check only by the rock pressure of the gas. If each cubic foot of gas were retained to perform its work of expelling petroleum the pressure would help to retard the water for a considerable period, or until the maximum amount of oil could be recovered. Huntley (b) cites the Hogshooter pool in Oklahoma as an example of a producing gas district that was ruined by having its gas drained too rapidly. Wells were constantly drawn upon to their utmost capacity; hence as no pressure restrained the water under high pressure in the lower part of the productive formation the water flooded one well after another.

FACTORS AFFECTING FLOW OF GAS AND OIL IN DIFFERENT SECTIONS OF THE SAME FIELD OR IN NEIGHBORING WELLS.

The concern of the operator of a plant for making gasoline of natural gas covers all phases of the industry from the occurrence of gas and oil in the well to the final disposal of the gasoline. Hence, in the following pages, is given a brief summary of some of the views that are held regarding the factors that affect the occurrence of gas and oil underground. These views are fully discussed in reports of the United States Geological Survey.

The operator is frequently puzzled to know why wells in one part of a field are more productive than are others in the same field, or why adjoining wells or wells on the same lease, are so erratic as regards output. Another question that may occur to him is why a particular field is productive and an adjoining territory non-productive. Many observations have shown that the strata yielding oil and gas are practically identical, the gas usually accumulating in the domes of the arches in the strata or in other elevated parts of the deposits. Gas almost invariably accompanies oil where conditions favor its accumulation, but oil is frequently found almost unaccom-

(a) Huntley, L. G., Possible causes of the decline of oil wells and suggested methods of prolonging yield: Technical Paper 51, Bureau of Mines, 1913, pp. 6-7.
(b) Huntley, L. G., op. cit., p. 7.

OCCURRENCE OF GAS AND OIL. 7

panied by gas on account of the collection of the gas in the highest portions of the strata or because of its escape through imperfections of the covering layers. Brine almost universally accompanies the oil and gas.

In addition to possessing a porous structure for holding the oil or gaseous contents, the reservoir rock must be entirely covered with an impervious layer, the commonest and most perfect cover being a fine-grained shale, whose imperviousness and freedom from fracture enables the "sand" to retain the gas or oil. Gas, oil, and water are frequently found distributed according to their specific gravities, gas disengaging itself from the finid and rising to the highest point in the beds, and water displacing the oil and finding a resting place as low down as possible. When oil and gas strata are comparatively little undisturbed, each well usually draws its supplies from a considerable area; indeed, the owners of wells in the United States are usually compelled to continue to raise oil, without regard to the conditions of market, to prevent its being obtained by neighboring leaseholders. On the other hand, faults and dislocations of strata may limit the area over which a single well draws its supplies, and so impede the free passage of the fluid Chat the pressure is small. It is now generally admitted that the pressures in wells are entirely due to accumulations of gaseous hydrocarbons, chiefly methane, which were formed with the liquid hydrocarbons and exist in a highly compressed condition and dissolved in the petroleum or accumulated in the beds immediately overlying the oil stratum. Where the gas has been allowed to escape freely, petroleum rarely flows from a well, and never, perhaps, unless left for a long time, rises to the surface unaided.

Discrepancy in production may in some cases be attributed to local variations of the reservoir rock, but Arnold and Garfias (a) state that an abnormally low production of oil can be traced to one or more of the following causes: Inefficient management; improperly finished well; poor condition of casing; failure to perforate casing, or inadequate size and number of perforations; obstruction of the bore-hole by tools or fragments of d~bris; failure to exclude water, which sometimes results in the inrush of sand; effect of neighboring wells; and drawing on a secondary sand only. Some of these causes affect the yield of gas also. Arnold and Garfias (b) add that although at some wells conditions can not be remedied, and at others the expense incurred would not be compensated by the added production, nevertheless, in most instances, an intelligent study of the trouble and its sources will disclose some comparatively simple means of improving conditions so as to increase the total yield.

(a) Arnold, Ralph, and Garfias, V. R., Methods of oil recovery in California: Technical Paper 70, Bureau of Mines, 1914, p. 9.
(b) Arnold, Ralph, and Garfiaa, V. R., idem.

8 CONDENSATION OF GASOLINE FROM NATURAL GAS.

EFFECT OF DRILLING NEIGHBORING WELLS.

Regarding underground connection between neighboring wells Huntley (a) has the following to say:

The first well drilled in a group will tend to set up drainage channels and divert large quantities of oil from a considerable area. Subsequent wells come in as much smaller producers than the original well. Again, in loose unconsolidated sands, such as are found in the Caddo field in Louisiana, and in the famous Glenn pool, in Oklahoma, if a well stops pumping for a day, the surrounding wells extend their own channels, breaking down the drainage systems of the first well, to the extent that it is often difficult to again recover oil from the well that has stopped pumping. As a result the wells in the Glenn pool are pumped 24 hours a day, 365 days in a year. The condition of the sand in the Glenn pool was brought about somewhat artificially by the use of enormous quantifies of nitroglycerin in shooting. The sand, originally coarse and porous, has probably been shattered throughout the entire producing area.

In certain lenticular formations, described by the oil man as "spotty," of two wells drilled only 150 feet apart, one has been a large producer and the other a dry hole. This discrepancy may be due to drainage conditions or may be caused by an intervening hard spot in the oil sand. If it is caused by drainage conditions, the stopping of the producing well would probably cause the other to produce. Again, wells 1,000 to 2,000 feet apart are in places so closely connected underground that the muddy water used in drilling one well has been pumped out by another well a considerable distance away, not necessarily the well nearest to the one being drilled.

Huntley (b) further states that in a tight sand neighboring wells do not affect each other to the same degree as in a very porous stratum; that is, such pronounced drainage channels toward the wells first drilled are not formed.

EFFECT OF FORMATION OF WAXY SEDIMENT.

Most of the plants for making gasoline from natural gas draw the gas from old wells, many of which are very small producers of oil. Hence many of them have not received much attention as regards upkeep. One result of this inattention is the formation of waxy sediment or paraffin. Regarding the formation of this waxy sediment Huntley (c) comments as follows:

Petroleum in the so-called paraffin-oil fuels consists of hydrocarbons of the paraffin series, which range from the heaviest oil to the lightest gas. The gaseous constituents of petroleum exist in what may be likened to solution, much like the gas of soda water, and as such expand and escape when the pressure is relieved by a well. The sudden expansion and volatilization of such light hydrocarbons has a refrigerating effect, like the expansion of ammonia gas in an ice machine, chilling the remainder of the liquid petroleum and causing the separation of the heaviest paraffin as a waxy sediment. This, along with water and fine rock sediments, clogs the pores of the sand and obstructs the passage of the oil into the well.

(a) Huntley, L. G., Possible causes of the decline of oil wells and suggested methods of prolonging yield Tectmical Paper 51, Bureau of Mines, 1913, pp. 23-24.
(b) Huntley, L. G., op. cit., p. 22.
(c) Huntley, L. G., op. cit., p. 6.

CONDENSATION OF GASOLINE FROM NATURAL GAS. 9

HISTORY OF THE MAKING OF GASOLINE FROM NATURAL GAS.

That gasoline can be extracted from natural gas has long been known, ever since o11 and gas have been noticed in some gas pipe lines, but the production of gasoline from natural gas has only within the past few years become of commercial consequence, owing principally to the ever-increasing demand for gasoline.

TWO SUCCESSFUL PLANTS IN 1904.

A. Fasenmeyer made gasoline from the gas of oil wells near Titusville, Pa., in the fall of 1904. His plant is almost within sight of the old Drake well. His first equipment was crude. The gas from the wells after passing through the gas pumps was cooled by means of a coil of pipe placed in a tank of water. The condensate produced was allowed to drip into a wooden barrel. The losses resulting from evaporation were large. The product when first collected had a gravity of 80 to 90 on the Baumé scale. His production the first year was approximately 4,000 gallons, for which he received 10 cents per gallon. Tompsett Bros., of Tidioute, Pa., claim to have preceded Fasenmeyer in the making of a commercial venture out of the process. They are operating successfully at the present time.

As these ventures proved a commercial success attention was turned to the designing of better plant equipment. Gas and oil operators in other oil fields in the United States proceeded to install gasoline plants.

EARLY METHODS.

At first common gas pumps, with pressures not exceeding 50 pounds per square inch, were used. Condensation was effected by running a pipe through the earth to the gasoline receivers. Mr. William Richards, of Warren, Pa., claims to have been the first to install high-pressure compressors. His first experiments, made in 1905, were with pressures of 400 pounds per square inch. Later he came to the conclusion that a pressure of 250 pounds per square inch was sufficient to make gasoline that was about right for shipping. Mr. Richards's plant was located at Mayburg, Pa.

In the first plants for making gasoline from natural gas the cooling system consisted in general of a series of pipes. In some plants the pipes were cooled by the air, but in most plants were immersed in tanks containing water or else the water was allowed to drip over the pipes. At most plants the collecting tanks were open to the atmosphere. The residual or waste gases were allowed to escape. After the condensate had "weathered "--that is, when the lighter fractions had been allowed to volatilize and escape into the atmosphere--the product was marketed.

10 CONDENSATION OF GASOLINE FROM NATURAL GAS.

LATER IMPROVEMENTS.

The next step in the industry was to pass the gases from collecting tanks from the single-stage compressor through a higher-stage compressor. The gases were again cooled. In this manner a second and more volatile product was obtained, which was mixed with the product from the first-stage compressor. This mixture was again "weathered'' and then marketed. F.P. Peterson, while connected with a gas-engine company in Grove City, Pa., claims to be the first to use the two-stage compressor method. As producers realized the great waste involved in this process, another improvement was introduced, as follows:

The condensate produced from both stages of compression and cooling, which had a gravity of 80 to 100 B., was mixed with refinery napthas until the specific gravity had been lowered to 60 to 76 B. By this means there was obtained a product that evaporated more slowly than did the condensate. The process of blending is more fully discussed elsewhere in this report.

The waste gases, after the gasoline had been extracted, were in part used for plant operation, and, in some plants, the remainder was returned to gas mains which supplied towns with gas for lighting and manufacturing purposes. In most plants the waste gases were allowed to escape into the atmosphere. At present much information is at hand as the result of the experimental work done, so that plants arc now installed to meet particular requirements. The advisability of employing single or double stage compressors, the pressures to be used, the method of handling and disposing of the condensate, and the disposition of the waste gases are all considered.

PATENTS ISSUED.

Chute (a) gives the various patents that have been taken out covering the condensation of the hydrocarbons in natural gas, as follows:

In 1866 Johnson received patent No. 54910 which clearly discloses the art of rendering liquid the vapors that rise with or are forced up with petroleum.

In the Heinzerling patent of 1897, No. 575714, which expired January 28, 1914, there is shown an air-compressor or gas-compressor cylinder and a gas-expansion cylinder, both coupled to a flywheel, with a series of condensers and heat exchangers between. The specification clearly explains that the gas is to be compressed in the first cylinder and cooled in two condensers in series, with condensation of the condensible liquids, which are removed by appropriate valved containers depending from and connected with the condensers. Thence the water-cooled gas passes to other condensers

(a) Chute, H. O., The patent processes for making casing-head gasoline: Jour. Met. and Chem. Eng., vol 12, No. 3, March, 1914, pp. 147 and 148.

PRODUCTION IN EASTERN PART OF THE UNITED STATES. 11

cooled by the residual gas, which is in the meantime expanded in the second cylinder, thus aiding the compression. The expansion produces cold gas which afterwards, circulating through the last condensers, cools the compressed gas to a point stated to be between - 25 and - 40 C. (- 13 to - 40 F.). The first water cooling is stated to refrigerate the gas to 10 C. (50 F.).

Among the earlier unexpired patents is No. 668197 of 1901, issued to Seceur, which claims a process of liquefying methane from natural gas.

In 1907 patent No. 867505 was granted to Dennis Hastings and W. Brink. It discloses that natural gas, after having been artificially compressed, is brought into contact with water which serves to cool the gas; later water or oil is atomized to intermingle with the gas to cool it. The claims are for an arrangement of apparatus.

In 1909, John L. Gray obtained patent No. 993976, for certain apparatus for obtaining gasoline from the casing-head gas. The claims are for an organization of apparatus for separating, first, any engine or cylinder oil from the gas by means of the ordinary steam trap or oil trap used on steam lines, a condenser with another oil trap beyond, and a relief valve which is an ordinary steam safety valve. There is also a pot steam trap to separate the condensed gasoline from the gas, and a receiving tank.

Chute (a) states that in the processes now in successful use the essential steps have been covered by expired patents.
Patents covering the separation of the light paraffin hydrocarbons in natural gas are described in the appendix at the end of this report.

PRODUCTION OF GASOLINE FROM NATURAL GAS IN THE EASTERN PART OF THE UNITED STATES.

In the Appalachian oil fields the utilization of casing-head gas for making gasoline is more extensive than in the Mid-Continent or California fields. The industry had its commercial inception in Pennsylvania and West Virginia. East of the Mississippi River the approximate number of plants in commercial operation was about 253 in July, 1913. The Plants were distributed among the various States about as follows: New York, 1; Pennsylvania, 100; West Virginia, 100; Ohio, 47; Illinois, 5. The industry in these States is firmly established, and new plants are being built even in places where many thought that installations would not be placed.

THE GASOLINE INDUSTRY IN WEST VIRGINIA.

The industry of making gasoline from natural gas has made fairly rapid progress in West Virginia in the past few years. In that State gasoline was first made from natural gas in 1905. There were

(a) Chute, H. 0., op. cit., p. 148.

CONDENSATION OF GASOLINE FROM NATURAL GAS. 12

in July, 1913, about 100 plants in the State. The production from 10 plants exceeded 500 gallons per day and from 5 exceeded 1,000 gallons per day. The production of the remaining plants ranged from a few gallons up to 500 gallons per day. The number of wells connected to each plant varies from 1 or 2 up to 100, with an average of about 15 to 20. Of the total number of oil wells in the State, about 1,500 are utilized for gasoline production. The production is confined almost exclusively to 12 counties--Brooke, Calhoun, Hancock, Harrison, Marion, Marshall, Pleasant, Richie, Tyler, Wetzel, Wirt, and Wood. The total production for 1913 was 7,662,493 gallons. (a) Hill (b) states that in 1912 there was produced 5,318,136 gallons.

Tyler and Pleasant Counties produce about 75 per cent of the total quantity of gasoline produced in the State. In Tyler County are five productive oil sands. The gas utilized for gasoline production accompanies the oil in the Big Injun sand. In Pleasant County the gas utilized is chiefly from oil wells tapping sands in the Berea grit. This sand lies below the Big Injun. The wells from which the natural gas is derived in these fields are from a few years to 20 years old, some of the first wells drilled still producing vapors of the heavy hydrocarbons. The highest pressures utilized for making gasoline in West Virginia are about 150 pounds per square inch, none being over 250 pounds. Two plants at Follansbee, W. Va., use the pressure last mentioned.

Of about 14,000 producing oil wells in the State approximately 1,500 are utilized for gasoline production. Day (c) gives 13,014 as the number of producing oil wells in the State at the end of the year 1911. This was an increase of 279 wells over the year 1910. At the present time the authors estimate that there are 14,000 wells in the State. This estimate is based only on what seems to be a reasonable increase in two years' time over the production for 1911 as given by the Geological Survey. The rate of increase in production for tile two years 1912 and 1913 is greater than during the preceding two years largely because the price of petroleum increased decidedly for a time.

THE INDUSTRY IN PENNSYLVANIA.

The industry in Pennsylvania during 1912 and 1913 has made rapid progress. At the close of 1913 there were nearly 100 plants in successful operation. The industry is confined almost entirely to the counties of Butler, Forest, McKean, and Warren.

Most of the plants are rather small, few producing 500 gallons per day. The average plant produces only about 200 gallons per day. The number of wells used for making gasoline is 1,100 or 1,200.

(a) Hill, B., Natural gas: Mineral Resources U. S. for 1913, U. S. Geol. Survey, 1914, p. 1481.
(b) Hill, B., Natural gas; Mineral Resources U. S. for 1911, U. S. Geol. Survey, 1912, p. 348.
(c) Day, D. T., Petroleum: Mineral Resources U. S. for 1911, U. S. Geol. Survey, 1912, p .351.

THE INDUSTRY IN CALIFORNIA. 13

There were in 1913 about 56,000 producing oil wells in the State. Day (a) gives 52,545 as the total number of producing wells in the State for 1911. The increase for the year 1912 was 1,645 wells and for 1913 was 2,065 wells.

The output of gasoline for the year 1913 was 3,680,096 gallons, (b). The production for 1912 was 2,041,109 gallons. (c) The drawback to development in the northern counties lies in the lack of satisfactory transportation facilities. Most of the gasoline is hauled in tank wagons to the refineries where it is blended with naphtha. Some producers are forced to haul their product as far as 15 miles in tanks. When better facilities shall have been provided for transportation, thereby cutting down considerably the cost of production, there will be a wider expansion in these oil fields. Less than 2 per cent of the producing oil wells are utilized for the production of gasoline, as against 10 per cent in West Virginia.

The gases available in the Bradford County and the Warren County fields are from the third oil sand. The gases from most of the wells issue under a few pounds pressure. A small area around Tidioute Pa., produces a gas consisting almost entirely of the vapors of the liquid hydrocarbons. These vapors are drawn out under a reduced pressure of 20 inches (12 pounds) of mercury. In no other field, to the authors' knowledge, are such "wet" gases encountered. The vapors after passing the vacuum pumps are simply cooled by means of running water. They are not compressed.

THE INDUSTRY IN CALIFORNIA.

PRODUCTION IN 1912.

Hill (d) states that the gasoline produced in California in 1913 was 3,460,747 gallons, valued at $405,186.

Gilmore (e) specifies the following production for California:

14 CONDENSATION OF GASOLINE FROM NATURAL GAS.

NOTEWORTHY INTEREST IN THE INDUSTRY.

Gilmore (a) says further, regarding the gasoline industry in California:

In the manufacture of this much-needed commodity [gasoline] more interest has been shown during the past year than in oil. Many experiments have been made and every theory brought forth and worked upon to bring out the greatest percentage possible in extracting the motor fuel from crude oil and gas. Refrigerating and freezing processes have worked overtime and enthusiastic estimates of the possibilities likely to be attained have been published, leading to the belief that the very air around an oil well would be converted into liquid, but from general observations made in the field most of these experiments are still in their incipiency. It has been demonstrated that low-gravity oil and its gas do not contain proportions of gasoline equal to those of the higher grade, and every effort to bring out and increase the percentage has been a failure. It is contended that the gas found in the Olinda field and worked out through the refrigerating process contains a larger percentage than could be given by the compressor method. This is a matter of theory alone. The "plant" so far has not proved its efficiency over the latter method and has fallen far short of expectations. They are making about 1,000 gallons per day. The same results and possibly better would have been obtained with the compressor system. They claim, however, that if the results are no larger the running expenses are considerably less.

In the Santa Maria field, where the gravity of the oil runs above 30 B., gasoline of the best gravity is manufactured from casing-head gas. The field is noted for its large amount of escaping gas, and during the past two years a number of plants have been installed. Each of these up to the present time has shown an increase rather than a decrease in output, and what is more the operation of these "plants" has shown a tendency to increase the amount of production in the wells from which the gas is taken, the result of the vacuum caused in draining out the gas.

MARKETING THE PRODUCT.

Nearly all of the production of casing-head gasoline is marketed in southern California. The coast towns, such as Santa Barbara, Santa Maria, and Ventura, get a liberal supply from the Santa Maria field. The Pinel-Dome people ship their product here and market from tank wagons; the Purity gasoline is shipped to a distributing station here and is marketed in the city and through adjoining towns and cities. The Union Oil Co. markets the product of the Pacific Co. and its own.

Investigations made prove that where the gravity is not lowered below 62 or 64 B. there is no perceptible difference between this article and that manufactured from crude oil. Wherever an inferior grade is placed on the market it is in every instance the result of reducing below the commercial grade by the application of too large a percentage of distillate, and this may happen to all grades. This is frequently the result of low prices being advertised, and until methods are adopted that will call for an inspector and impose a penalty for selling anything below a given specific gravity these dishonest methods will probably continue. These adulterations are brought about by the retailers, and not by the manufacturers, it is claimed.

Regarding immediate future developments Mr. Gilmore, in a letter to the authors, states that "the Union Oil Co. expected to extract with a new installation about 8,000 gallons per day from 8,000,000 cubic feet of gas, and a new plant owned by A. F. Gilmore is expected to add another 1,000 gallons per day, making a total of 25,450 gallons per day."

(a) Gilmore, Frank, Gasoline in California: Oil and Gas Jour., vol. 12, Oct. 9, 1913, p. 30.

THE INDUSTRY IN CALIFORNIA. 15

DISTRIBUTION OF PLANTS.

Laney (a) writes as follows regarding the production of gasoline in California.

The coast-range mountains divide the State into two great groups known as the coast fields and the interior or valley fields. In the former group are the Santa Maria Venture, Newhall, Salt Lake, and Fullerton-Whittier, while the Coalinga, Lost Hills, McKittrick, Kern River, Sunset, and Midway fields comprise the latter group. The valley fields have but one gasoline plant and that inoperative, while every field in the former group has one or more plants either in the course of construction or having been in actual operation for a year or more. And this in spite of the fact that production of both gas and oil in the valley fields is many times greater than that from the fields to the west of the mountains. That not all the gas is suitable for gasoline production is true, but it will undoubtedly be found when a thorough examination is made of these gases that the volume carrying considerable gasoline constituents is as great if not greater than in all the rest of the State taken together. The total number of gasoline plants in these fields is, at the present writing, 16, having a capacity in excess of 24,000,000 cubic feet of gas and producing upwards of 25,000 gallons of this valuable commodity daily.

METHODS EMPLOYED.

In general the methods employed in recovering the condensible fraction from the gases in these fields are similar to those used elsewhere in the country, the variations being due to differences in local conditions. A great deal of the gas worked is obtained from flowing wells in combination with the oil and is separated in gas traps, being lead-line rather than casing-head gas. Naturally this gas is often far from clean, and in some cases leaves the trap at high temperatures (100 to 120 F.--38 to 49 C.), and it has been found necessary to use some form of precooling to lower the temperature before leading the gas to the machine, and in many cases scrubbers have been employed in order to remove the heavier distillates and any foreign matter that might work harm to the compressor cylinders and valves.

The pressures used run generally from 210 to 250 pounds per square inch, with the exception of one plant using an ammonia refrigerating system where the product is obtained at 40 pounds pressure. There is one plant using three-stage compression; the majority use .two-stage, but since their final pressures are 250 pounds the only apparent advantage of this variation is that they get one more cut in their product, and this advantage disappears when, as is done in most cases, the different cuts are all run into one stock tank and allowed to blend.

The problem of final cooling of the compressed gas has been approached in a variety of ways, chief among which are, first, by allowing the compressed gas to expand through a controlling valve or an orifice around the pipe containing the incoming compressed gas; second, by means of an ammonia refrigerating plant, auxiliary to the main plant; and third, by expanding the compressed gas through a power cylinder and using the power thus made available for any one of a variety of purposes around the plant, such as redistributing the residue gas over the lease, assisting in the operation of the main compressor or operating another low-pressure compressor cylinder in parallel with that of the main machine. This third method seems to be by far the most practical, where low temperatures are desirable, for not only can as low or lower temperatures be obtained by this method as by either of the other methods, but a part of the power expended in the main engines in compressing the gas is here recovered and put to some useful purpose. The principal difficulties so far encoun-

(a) The production of natural gasoline in California. The Bessemer Monthly, December, 1913, p. 1.

16 CONDENSATION OF GASOLINE FROM NATURAL GAS.

tered in dealing with the extremely low temperature obtained in this expanding cylinder, frequently aslowas-50 to -60 F. (-46 to -51 C. ), have been those of lubrication and obstruction due to congealed moisture. The former can usually be overcome by using a good grade of low-temperature oil and by exercising care in so feeding this oil to the cylinder and valves that it is applied directly to the surfaces in contact. The problem of removing all moisture from the gas before allowing it to enter the expanding cylinder is not, in all cases, so simple as would appear, for in spite of the fact that the temperature of this gas before expansion is several degrees below the freezing point of water, a certain amount of moisture sometimes persists in spite of all efforts to trap it out and later freezes either in the expanding cylinder or, as is more frequently the case, in the double cooling coils, necessitating the application of heat from time to time to thaw them in order that the operation may continue. To eliminate the possibility of shutdowns from this cause it has been found necessary in some cases to install double coils in duplicate, so that one half may be shut down for thawing without seriously disturbing the operation of the plant. A little warm high-pressure gas led to these coils has proved a very simple and convenient means of removing this accumulation of frost.

DETAILS OF EQUIPMENT.

With lower temperatures has come a recognition of the value and importance of thorough insulation of all piping through which this low-temperature gas is handled. This insulation is usually accomplished by boxing the coils and packing with dry sawdust, while all other piping is covered with a good grade of molded cork insulation. The finer details of construction and operation such as this were neglected during the earlier attempts at the recovery of gasoline, but their importance is now being fully recognized, and in the most up-to-date plants all condensing equipment following the water-cooling coils is housed and the piping carefully insulated.

The value of automatic traps, for handling the gasoline from the accumulators as fast as it is condensed, in order to eliminate as far as possible the solution of compressed gas in the product, is rapidly being appreciated, and at many plants the vapor tensions and evaporation losses have been materially reduced by the adoption of these simple devices.

IMPORTANCE OF WATER SUPPLY.

Another obstacle that the California operators have had to overcome is the difficulty of obtaining water in sufficient quantities and of such temperature as is necessary for cooling purposes. Water must be carefully conserved, for most of it is brought from some outside source and water bills form no small item in the operating expenses of a plant. This conservation has been accomplished by using the same water over and over again, pumping it through cooling towers and reducing its temperature by evaporation before leading it again over the cooling coils and through cylinder jackets. Only enough new water is added from time to time to make up for evaporation losses and those due to unavoidable leaks.

SPECIFIC GRAVITY AND PRICE OF PRODUCT.

The gravity of the product obtained varies greatly, running as low in some cases as 67 B., while in others it varies between 85 and 90 B., this gravity being the blend of all the cuts from any one plant.

The price obtained for the unblended product ran in the neighborhood of 10 cents at the plant, but some of the larger operators are doing their own blending, and marketing a resulting product at 62 B. that brings them from 15 to 17 cents, thus realizing the maximum return from the production of their plants.

CONDENSATION OF GASOLINE FROM NATURAL GAS. 17

THE INDUSTRY IN THE MID-CONTINENT FIELD.

DETAILS OF PRODUCTION.

In the Mid-Continent field the first plant was installed in 1909 by D. W. Franchot at Kiefer, Okla. At the close of the year 1911 there were 7 plants in operation, making about 2,000 gallons of gasoline daily. In June, 1913, there were 23 plants. Table 1, following, shows the location of some of the plants in the Mid-Continent field on June 1, 1913, the quantity of gas used, the number of wells used, the number of compressor units, the reduced pressure to which gas is subjected when drawn from the wells, the compression to which the gas is subjected in the compressors, the quantity of gasoline produced, the gravity of condensate in the accumulator tank, the purpose for which the condensate is used, the value of the plant, and the quantity of the gasoline sold. Complete returns were not obtained.

QUANTITY AND VALUE OF CONDENSATE.

These plants, with others in Oklahoma not listed in the foregoing table, produced about 350,000 gallons of natural-gas condensate during April. The value of the condensate is estimated at $35,000,

18 CONDENSATION OF GASOLINE FROM NATURAL GAS.

about 500 wells being utilized. At the close of May, 1913, there were in Oklahoma 25,612 producing oil wells, making about 4,000,000 barrels of oil, worth $3,520,000, at 88 cents a barrel, the price then prevailing. If the average percentage of gasoline obtainable from Oklahoma crude oil by refining is estimated to be 14, then 23,520,000 gallons of gasoline could be produced, which, at the rate of 15 cents per gallon, would he worth $3,528,000.

Gas from about 2 per cent of the total oil wells was used for making gasoline. The gasoline made from casing-head gas was probably less than 1 per cent of the gasoline produced at the refinery.

At the end of the year 1913 there were 40 plants in operation ill Oklahoma. The value of gasoline produced in 1913 was $577,944 (a).

FUTURE OF THE INDUSTRY IN OKLAHOMA.

It has been stated that about 25,000 producing wells were in operation oil the last day of May, 1913, and that 500 were used for gasoline production. It is not to be inferred that all of these wells will contain gas of sufficient volume or proper character to produce gasoline.

Probably less than one-third of the total number of wells will be available, owing to the reasons following. These reasons also apply of course to other localities in the United States.

(1) Insufficient gas yield.

(2) Unfavorable location of wells with reference to transportation of finished product.

(3) Poor quality of gas.

On the other hand, gas from many wells that have not been utilized as yet will produce gasoline in paying quantities. Many wells that do not produce gas of proper character now will do so in the future as the wells grow older. This statement is substantiated by the experience of many operators in the Appalachian fields. There the old wells are producing gas that is the richest in gasoline vapors. The final maximum yield per 1,000 cubic feet of gas will be reached when the minimum pressure is reached in the oil well. The gasoline yield should then become practically constant.

The Muskogee, Okmulgee, Cushing, and Cleveland oil fields in Oklahoma possess many wells that are promising. The outlook for large producing wells in the north of the State is not so promising. Seemingly there is not enough gas in many territories to warrant the installation of gasoline plants. There are, however, many favorable locations, and to date those plants that have been developed in the northern region are profitable notwithstanding the small size and great number of wells connected.

(a) Hill, B., Natural gas: Mineral Resources U. S. for 1913: U. S. Geol. Survey, 1914, p. 1481.

TOTAL GASOLINE PRODUCTION IN THE UNITED STATES. 19

DEVELOPMENT OF INDUSTRY IN FOREIGN COUNTRIES.

Development of the industry in foreign countries has been slow. The authors have knowledge of one plant at Payta, Peru, installed by Americans. The plant handles 60,000 cubic feet of gas per day. Another small plant in the Galicia oil fields, Austria-Hungary, handled 20,000 cubic feet of gas per day.

TOTAL GASOLINE PRODUCTION IN THE UNITED STATES.

PRODUCTION IN 1911 AND 1912.

The following table, covering gasoline production in the United States for 1911 and 1912, is taken from data compiled by Hill: (a)

PRODUCTION IN 1913.

The data following show the production of gasoline from natural gas for the year 1913. The figures are taken from data obtained by the United States Geological Survey. (c).

(a) Hill, B., Natural gas: Mineral Resources U. S. for 1913, U. S. Geol. Survey, 1914, pp, 1479-1480.
(b) Natural condensation in the pipes.
(c) Hill, B., Op. cit.

20 CONDENSATION OF GASOLINE FROM NATURAL GAS.

According to these figures the increase in the production of gasoline from nature gas in the United States for the year 1913 over the year 1912 was about 100 per cent. According to the United States Geological Survey figures, the rate of increase for 1912 over 1911 was 63 per cent.

According to Hill, the total estimated consumption of natural gas in the United States in 1912 was 562,203,452,000 cubic feet, (a) and the total quantity used for making gasoline was 4,687,796,329 (b). This latter figure represents gas not included in the total consumption, for it covered gas principally going to waste. At the close of the year 1913 (b) this figure was 9,899,441,500 cubic feet and the total quantity of gas used for all purposes was 581,898,239 cubic feet (a).The percentage of natural gas used for making gasoline was 1.7.

CHEMISTRY OF NATURAL GAS.

In the gasoline industry natural gas is popularly classified in two great divisions--"wet" gas and "dry" gas. Gas not intimately associated with oil is known as "dry" gas; that in the same stratum with oil and in intimate contact with it is the so-called "wet" gas, from which gasoline is condensed. As the result of many analyses, the Bureau of Mines finds that natural gas is a mixture in which the hydrocarbons of the paraffin series predominate and that small proportions of nitrogen, carbon dioxide, and water vapor are present. In a few samples of natural gas the bureau has found that the carbon dioxide may amount to as much as 10 per cent; in one sample it amounted to 31 per cent. Another natural gas examined contained 97.9 per cent of nitrogen, 0.10 per cent of carbon dioxide, and 2 per cent of methane. Hence the proportions of carbon dioxide and nitrogen may in exceptional samples be large.

Carbon monoxide, hydrogen, hydrocarbons of the olefin series, or other gases that most textbooks state are constituents of natural gas are not present. Hydrogen sulphide is found in some natural gas.

NATURAL-GAS ANALYSES MADE BY THE BUREAU.

The results of some natural-gas analyses made by the bureau are shown in Table 2, following. They are given to show the variation in composition of different samples of natural gas:

(a) Hill, B., Natural gas: Mineral Resources U. S. for 1913, Geol. Survey, 1914, p. 1414.
(b) Hill, B., op. cit., p. 1480.

CHEMISTRY OF NATURAL GAS 21

22 CONDENSATION OF GASOLINE FROM NATURAL GAS.

CHEMISTRY OF NATURAL GAS. 23

NOTES.

Sample 1871.--The gas sampled comes from the fourth sand, which is 800 feet deep. The rock pressure in the well was 300 pounds per square inch. The capacity of the well was 3,000 cubic feet of gas per day.
Sample 1889.--The sample came from the third sand. Five gas wells were tapped by the pipe line from which the gas sample was drawn. The rock pressure at the wells was 62 pounds per square inch.
Sample 1872.--Collected in Clarion County, Pa., near the town of Mill Creek. The sample came from the Bradford or Little Bradford sand, which is 2,100 feet deep. The rock pressure was 850 pounds per square inch and the capacity of the well 3,000,000 cubic feet a day. This gas contains a higher percentage of the heavier paraffin hydrocarbons than does the gas represented by sample 1871 that comes from the shallower sand.
Sample l848.--The sample was collected at well No. 14 of the A. W. Starr farm. The gas is from the Speechley sand.
Sample 1838.--The sample was collected from the No. 1 well on the J. S. Somerville farm. The gas comes from the fourth sand.
Sample 3177.--The sample was taken from the Collinsville pipe line in the pumping station of the Kansas Natural Gas Co. at the north end of the Hogshooter field. This line tapped about 40 gas wells. The initial rock pressure of the wells was 490 pounds per square inch. At the date of collection of the sample the pressure had dropped to 120 pounds. This was one of the few samples of natural gas analyzed by the bureau that contained only methane as the combustible constituent when the sample came from a sand in close proximity to sands producing oil. Most gas from the oil regions contains other paraffin hydrocarbons besides methane, and gas coming from the same sand as the oil invariably contains other paraffin hydrocarbons. It is difficult to explain the presence of an enormous quantity of methane gas, such as is contained or was contained in the Hogshooter pool, in close proximity to oil sands. If gas and oil were of common origin in the particular region, one would suppose that the Hogshooter gas should contain higher members of the paraffin hydrocarbons than methane, as do the gases from neighboring oil wells. The phenomenon might be connected in some way with the movement of the gas through strata whereby ethane and still higher paraffin hydrocarbons were separated.
Sample 2121.--The sample represented a casing-head gas from the Glenn sand. It was collected about 2,000 feet east of the railroad station at Kiefer, Okla.
Sample 2445.--The sample was collected at the Cully well on the Ellis farm. The well was 340 feet deep and was drilled in 1903. A large amount of hydrogen sulphide was present in the sample. The determination of the hydrogen sulphide was made by absorbing the H2S in a standard iodine solution and titrating with a standard sodium thiosulphate solution. Other sulphur compounds may have been present; hence the assumption that 2.9 per cent was all H2S may be wrong. The gas possessed the odor of H2S.
Sample 2444.--The sample was obtained in the same locality as sample 2445, but from a different well. The well was 280 feet deep. Both wells were drilled in 1903. The hydrogen sulphide content of this sample is much smaller than that of sample 2445.
Sample 1031.--The sample is classified as a marsh gas in distinction from those gases that are found in the oil field and contain appreciable quantities of the higher paraffin hydrocarbons.
Sample 1033.--The sample was collected at a near-by seepage in the same locality. The gas was simply bubbling up through marshy ground.
Sample 1063.--The sample was collected from a slough on the Brown farm. It also represented a marsh gas.
Sample 1893.--The sample was collected from 15 oil wells, Nos. 1 to 15, of the Atlantic Refining Co. (South Penn Oil Co.).

24 CONDENSATION OF GASOLINE FROM NATURAL GAS.

Sample 1066.--The striking feature of this sample is the high percentage of nitrogen. A well had been drilled and the gas was issuing from it in considerable quantity. For present purposes to which natural gas is put, the gas would of course be worthless.
Sample 1378.--The sample was collected from a slough about 15 feet in diameter. It represented what was seemingly another marsh gas.

The last eight samples given in the t able were taken from natural gas supplied the city in which the sample was obtained.

COMMENTS ON THE ANALYSES.

It will be observed that the samples ranged in heating value from 724 to 1,657 British thermal units per cubic foot at 0 C. and 760 mm. normal pressure, except one sample which had the abnormally low heating value of 21 British thermal units per cubic foot.

The analytical results show only approximately the quantity of the individual hydrocarbons, although the percentages of total paraffin hydrocarbons are correct. The heating values of the samples, as calculated from the analyses, are also correct. A discussion of natural-gas analyses is found in Bulletin 42 of the Bureau of Mines. (a) The causes of erroneous results that are frequently reported are there explained.

METHOD OF ANALYSIS USED.

The ascertaining of the exact proportions of the different hydrocarbons that may be found in natural gas has long been a stumbling block in gas analysis. The ordinary eudiometric method of analysis offers little in the way of a complete separation of a natural gas into its various constituents. Determination of the total paraffin-hydrocarbon content, with an approximate determination of the individual paraffins present, has been the only end attained. The Bureau of Mines in working on this problem succeeded in separating a natural gas into its individual paraffins by means of fractional distillation at low temperatures. Natural gas was first liquefied by means of liquid air, and then separated into its constituents by fractionation in vacuum at different temperatures.

The results of a complete analysis, including the quantity of each paraffin hydrocarbon found by the above method follow. For comparison, the results of an eudiometric analysis of the natural gas of Pittsburgh are also included.

(a) Burrel, G. A., and Selbert, F. M. The sampling and examination of mine gases and natural gas, 1913, 116. pp.

CHEMISTRY OF NATURAL GAS 25

Included in the nitrogen content of the above analyses is 0.03 per cent of carbon dioxide present in the natural gas. The natural gas supplied to Pittsburgh can not be used for the commercial production of gasoline, although it contains sufficient of the higher paraffin hydrocarbons, the butanes, pentanes, and hexanes, to produce some condensation (drip) in the pipe lines in the winter time. These hydrocarbons are present in small quantity, as shown by fractionation experiments conducted by the bureau. It is only because of the immense volume of gas passing through the lines that appreciable condensation of vapor occurs.

A "wet" natural gas from which gasoline is obtained commercially was also subjected to fractionation.(a) The results follow:

PROPERTIES OF THE PARAFFIN HYDROCARBONS.

The properties of those hydrocarbons of the paraffin series that concern the gasoline industry are given below:

(a) A technical paper covering in detail, this method of separating gases and the results of experiments by the bureau is being prepared.
(b) Holleman A. F., Organic chemistry, edited by A. J. Walker, 1910, p. 41.
(c) Landolt and Bornstein, Physikalisch-chemische Tabellen 3d ed. 1905, pp. 416, 425 (J. Thomsen).
(d) Gas at ordinary temperature.
(e) Wright, L. T. Illuminating power of methane; Jour. Chem. Soc., vol. 47, 1885, p. 200.
(f) Landolt and Bornstein, Physikalisch-chemische Tabellen, 3d ed., 1905, pp. 185 (Dewar).
(g) Landolt and Bornstein Physikalisch-chemische Tabellen, 3d ed., 1905, p. 185 (Olszewski).
(h) Frankland, P., Illuminating power of methane: Jour. Chem. Soc., vol. 47, 1885,p. 235.
(i) Landolt and Bornstein, Physikalisch-chemische Tabellen, 3d ed., 1905, p. 182 (Dewar).
(k) Liquid at ordinary temperature.

26 CONDENSATION OF GASOLINE FROM NATURAL GAS.

Methane, ethane, propane, and butane, as shown by the above table, are gases under ordinary atmospheric conditions. Pentane, hexane, and heptane are liquids and are the chief constituents of ordinary refinery gasoline. Of the four gases mentioned, methane is the most difficult to liquefy. At any temperature below -160 C. it becomes liquid when its pressure is 1 atmosphere. The boiling point of the liquid is -160 C. Above -160 C. greater pressures are necessary to liquefy methane, until at a temperature of -95.5 C. a pressure of 735 pounds per square inch is required. These two values are the critical temperature and the critical pressure, respectively, for methane. No matter what the pressure applied to the gas methane, it can not be liquefied at a temperature higher than - 9.5.5 C. The above general statement holds true for all gases. They can be liquefied at atmospheric pressure if the temperature is lowered sufficiently, but great pressure will not accomplish the liquefaction until the critical temperature is reached. Ethane (critical temperature, 35 C.; critical pressure, 664 pounds per square inch), it will be observed, is more easily liquefied and in the liquid condition has a higher boiling point (-93 C) than methane.

Propane (critical temperature, 97 C.; critical pressure, 647 pounds per square inch) is more easily liquefied than methane or ethane.

Butane, the critical constants of which have not been determined, must be still more easily liquefied than the three already mentioned, because in the liquid condition it boils at 1 C.

OCCURRENCE OF GASOLINE IN CASING-HEAD GAS.

When a gas bubbles through or comes in contact with a liquid, it takes up and carries along vapor or minute particles from that liquid. The proportion of vapor increases as the temperature rises, and is quite independent of the nature of the gas as long as no chemical action takes place. When a natural gas in the earth comes in contact with petroleum, those fractions of the petroleum having the lower boiling points are principally taken up, inasmuch as their vapor pressures are much higher than those of the other fractions. If the well is under reduced pressure, products with higher boiling points will also be removed in the gas. The vapors are carried with the gases mentioned, in the same manner that water vapor exists in air.

At any particular temperature a fixed quantity of water vapor will be found in the atmosphere if the latter has reached complete saturation, a condition that seldom prevails. Usually a limited supply of water has been encountered by the air, and the atmosphere is spoken of as having a certain relative humidity, meaning that the saturation is incomplete at the existing temperature, or that more water vapor could exist in the air were a source of moisture available. In similar manner gases in an oil well mix with heavy

OCCURRENCE OF GASOLINE IN CASING-HEAD GAS. 27

hydrocarbon vapors. The amount of vapor carried will depend on the temperature and pressure existing in the earth, on the readiness with which the vapors can be obtained, and on the gasoline content of the crude oil in the well. A certain maximum quantity of the heavy vapors will issue with the gases from a well under given conditions of temperature and pressure. The intimateness of contact between the oil and the gas is an important factor. The maximum content, or condition of complete saturation, is probably by no means generally prevalent. The porosity or closeness of the strata, the depth of the well, and the rapid expansion of the gas from the casing head cause variations in the temperature of the gas. The pronounced temperature effects, of course, appreciably change the capacity of the gas to hold gasoline vapor. Such rapid expansion of gas from a casing head may occur as to cause a heavy condensation of vapor at the casing head, owing to a lowering of the temperature of the gas.

At some operations, wells have been under reduced pressure for a long time, so long, in fact, that only small quantities of the four permanent gases already mentioned are left in the strata. Under such conditions the mixture that comes from the well may consist almost wholly of vapors of the liquid hydrocarbons, unless air has been drawn into the strata, owing to the reduced pressure.

RELATION OF THE CHARACTER OF OILS IN THE SAND.

The yield of gasoline from natural gas is largely determined by the proportion of the vapor of the liquid paraffins in the gas mixture. Therefore the character of the oils in a sand is of importance.

Crude oil (petroleum) is a mixture of closely related complex hydrocarbons and of various other organic substances. There are many different compounds (isomers) corresponding to a particular molecular weight, and the boiling points of those isomers lie so closely together that their separation by fractional distillation is impossible. The liquid hydrocarbons that mainly concern the gasoline industry are the pentanes, hexanes, and heptanes. However, small quantities of even higher homologues are undoubtedly obtained.

Some information as to the gasoline content of a natural gas can be gained by determining the proportion of light constituents in the oil with which the gas is associated.

Many investigations have shown that the gasoline constituents for many oils range from zero to 30 or more per cent of the total volume of the oil. Consequently, many oils are so heavy and their vapor pressures so low at existing earth temperatures that the proportion of vapors to be derived from them is too small to warrant the installation of a plant.

The table following shows the vapor pressures of the liquid paraffin hydrocarbons at various temperatures.

28 CONDENSATION OF GASOLINE FROM NATURAL GAS.

From the table it may be inferred that the chief liquid constituents of gasoline made from natural gas are the pentanes and the hexanes as their vapor pressures at any temperature are far greater than those of the other liquid hydrocarbons.

EFFECT OF PRESSURE AND TEMPERTURE ON GASES IN THE STRATA.

Natural gases in the oil fields of the United States are principally mixtures of methane, ethane, propane, and butane. Methane is always present in a well in the gaseous condition. Ethane becomes a liquid at a temperature of 35 C. under a pressure of 664 pounds to the square inch. Hence if a natural gas consisted of ethane only and was subjected to a pressure in the earth greater than 664 pounds, it would be in the liquid condition.

The authors have no evidence that ethane occurs in anywhere near the pure condition in the earth. As the proportion of ethane in a mixture decreases, there is required a proportionally greater pressure than 664 pounds to liquefy it. If a sample contained 50 per cent ethane and 50 per cent methane, there would be required a pressure of at least twice 664 pounds, or 1,328 pounds, to liquefy the ethane at 35 C., and to liquefy the methane a pressure of at least twice 735 pounds, or 1,470 pounds, at -95.5 C. Moreover, a temperature of -95.5 C. is far below that prevailing in oil and gas sands. A pressure of 1,328 pounds per square inch is probably unknown in the gas fields, but pressures as high as 800 to 1,000 pounds have been measured. Propane and butane are each more easily liquefied than ethane.

The critical temperature of propane is 97 C., and its critical pressure is 647 pounds per square inch. According to analyses made by the authors the amount of propane in most natural gases is less than that of ethane, so pressures sufficient for its liquefaction do not exist in the sands penetrated by wells.

The natural gas of Pittsburgh according to liquefaction experiments made by the authors, contains about 84.7 per cent methane, 9.4 per cent ethane, 3.0 per cent propane, 1.3 per cent butane, (chiefly),

OCCURENCE OF GASOLINE IN CASING-HEAD GAS. 29

and 1.6 per cent nitrogen. To liquefy the methane in this mixture at a temperature of -95.5 C. would require a pressure of at least (100/84.7)735, or 868 pounds. To liquefy the ethane at 35 C. there would be required a pressure of (100/9.4)664 or 7,064 pounds, and to liquefy the propane at 22 C. there would be required a pressure of (100/3)132.3 or 4,410 pounds. It will be noted that the critical temperature of methane is so low that under no condition could one conceive of its being liquefied in the earth. The critical temperature of ethane is a temperature that prevails in some rock strata, but the amount of ethane present in natural gas is invariably so small that pressures much higher than those found in rock strata would be required to liquefy the ethane.

As the temperature of a gas is lowered from its critical temperature, less pressure is required to liquefy it until finally at a certain temperature it becomes liquid at ordinary pressures. Propane has a critical temperature of 97 C. This temperature is higher than that ordinarily found in the sands of oil or gas fields, where a thermal gradient of 1 C. for each 60 or 70 feet of depth may be assumed. The temperature has to be -45 C. at ordinary pressures, however, for liquefaction to occur. Such a temperature is much lower than rock-strata temperatures. At 22 C. there is required a pressure of 4,410 pounds.

It follows that temperatures found in rock strata are not low enough, that rock pressures are not high enough, and that the amount of' propane in natural gases is too small to allow the existence of liquid propane in the sands penetrated by wells.

Butane gas becomes liquid at 1 C. at a pressure of 1 atmosphere. Its critical constants have not been determined, so far as the authors are aware. Its liquefaction point at ordinary pressures (15 pounds per square inch) is much closer to normal temperature than the liquefaction points of the three paraffin hydrocarbon gases already mentioned. Hence, if it constituted the whole of a natural gas, one could easily conceive that it would occur in the earth in the liquid condition. But in many natural-gas mixtures it appears to be present in even less amount than the other three gases. In Pittsburgh natural gas it is present in a proportion equal to about 1.3 per cent. With this quantity present, it would require a pressure of 1,077 pounds per square inch at 1 C. for liquefaction. At the higher temperatures of gas sands greater pressures would be required. If present to the extent of 20 per cent there would be required a pressure of 75 pounds at 1 C., and if it constituted 50 per cent of a gas a pressure of 30 pounds would be required. Gases that are used for

57858--Bull. 88---15----3

30 CONDENSATION OF GASOLINE FROM NATURAL GAS.

the condensation of gasoline usually issue from the earth either under reduced pressure, atmospheric pressure, or just above atmospheric pressure. In exceptional instances the pressure may be 50 or even 100 pounds, but at most plants the gas used issues from the wells under reduced pressure. In those gases that are used for gasoline condensation, butane, and also propane and ethane, are found to be present in greater proportions than in the so-called "dry" gases that issue under much pressure and are so largely used for heating and lighting towns. The authors believe that butane may be present in the "wet" gases to the extent of 10 per cent. Hence one can conceive that the amount of butane may be high enough, also the rock pressures high enough and the earth temperature low enough, so that in some sands butane may be present in the liquid condition. But if reduced pressures prevail in wells, as in most wells used for gasoline condensation, the rock pressures are usually too low, even if the partial pressure of the butane in the gas mixture is high, to permit liquefaction to take place.

In summarizing, one may say that at those wells from which gas is drawn for gasoline condensation, the three gases, methane, ethane, and propane, invariably occur in the earth in tile gaseous condition. Butane probably occurs as a gas in some places, but in others it is present as a liquid.

The question has been raised frequently as to whether natural gases are not accumulated as liquids in the underground reservoirs. If such were the case it would be possible for a single, comparatively small subterranean reservoir to yield for many years much larger quantities of gas than such reservoirs do yield.

As regards Pittsburgh natural gas and other similar gases that issue under considerable pressure from strata, none of the gaseous constituents present is liquid in the earth. However, where gases are associated with petroleum in the same strata, under heavy pressures, there is considerable solution of the gases in the oil. The natural gas used in Pittsburgh is not associated with oil in the earth.

TESTING NATURAL GASES FOR GASOLINE CONTENT.

Before plants are erected for the purpose of extracting gasoline from natural gas the yield and quality of the gas should be thoroughly investigated. Also of much importance is the marketing of the gasoline.

CLASSIFICATION OF KINDS OF NATURAL GAS.

As stated before, as regards the making of gasoline, natural gas is popularly classified in two divisions--" wet " gas and "dry" gas. This classification has come largely into general use with the development of the gasoline industry. Between the two classes there is no sharp line of demarcation.

TESTING NATURAL GASES FOR GASOLINE CONTENT. 31

"DRY" NATURAL GAS.

Some natural gas contains only methane as the combustible constituent and according to the above classification may be considered the driest of natural gases. This kind of gas is rare in the oil fields, but is common in gas fields, or in marshy districts unassociated with oil. The Hogshooter pool of Oklahoma, according to tests made by the bureau, produces a natural gas that contains methane as the only combustible constituent.

This kind of gas is found in States or districts in which oil has never been found. Incidentally it might be mentioned that the occurrence of such gas naturally escaping from the surface of the earth affords some proof of the nonexistence of oil. However, the indication is not infallible, because some natural gas that contains only methane as the combustible constituent is found in the oil fields. This gas comes from sands that do not bear oil.

The next grade in the transition of "dry" to "wet" gas may be considered that at present obtained from the Appalachian oil fields and used in Pittsburgh, Pa., and other cities. This natural gas issues under considerable pressure from wells in or near the oil fields. It has varied little in composition from the figures given on page 24 for the three years that the Bureau of Mines has been testing it. Air has never been detected in the samples tested. Many wells are abandoned yearly by the company that furnishes the city the supply, and new wells are drawn upon, the wells being abandoned when the rock pressure becomes so low as to be insufficient to assist in forcing the gas to Pittsburgh and ther points of consumption, or when the yield becomes too small even with the gas pumps that are used. In composition this gas is typical of the natural gas supplied to many cities. All of the ingredients present are gases at ordinary temperatures. Traces of butane and even of higher paraffin hydrocarbons are present--enough because of the many thousands of cubic feet of gas transported daily, especially in the winter time, to cause some condensation of vapors or drip, in the pipe lines. This gas has been said to pass at the rate of a mile a minute through mains connecting the wells to Pittsburgh. The drip is not sufficient to indicate that the gas is of value for gasoline extraction.

"WET" NATURAL GAS.

As to the so-called "wet" gas, or that from which gasoline can be extracted in quantity sufficient to warrant the installation of a plant, the proper testing of such gas in order to determine its gasoline content is of much importance. In the early days of the gasoline industry some failures of plants to fulfill expectations were due to inadequate testing of the gas before the construction of the plant had begun.

32 CONDENSATION OF GASOLINE FROM NATURAL GAS.

METHODS AND EQUIPMENT USED IN TESTS.

At present, tests have become better standardized, and there is scarcely any excuse for the failure of a plant because of inadequate preliminary tests. By itself, the ordinary eudiometric analysis is of little value for determining the gasoline content of natural gas. Moreover, it is extremely difficult to make, and the authors are safe in saying that a gas analyst must have had experience in refined analytical methods before he can make a satisfactory analysis of natural gas, especially of "wet" gas. In addition, the ordinary gas-analysis determination informs one only of the two predominating paraffins present but gives slight knowledge of the quantity of gasoline vapors. Early in the history of the industry, gas analysts turned their attention to other more easily conducted and more definite tests. Those laboratory methods adopted and at present in chief use have to do with solubility and specific-gravity tests.

SOLUBILITY TESTS

Natural gases are soluble in various solvents, such as alcohol, claroline oil, olive oil, kerosene, sperm oil, and rape-seed oil, in proportions depending upon the amount of hither paraffin hydrocarbons present in the gas mixture. All of the solvents mentioned have been used. F. P. Peterson, of Tulsa, Okla., informed the authors that he found it expedient to use claroline oil.

USE OF CLAROLINE OIL.

The Bureau of Mines methods of testing are described in Bulletin 42 (a) of the bureau. In using claroline oil the following procedure is adopted: 35 c. c. of the oil is placed over mercury in an ordinary Hempel gas pipette, and 100 c. c. of the natural gas to be tested is shaken with the oil until no further absorption of the gas mixture occurs. It was found that many natural gases from which gasoline is at present commercially obtained were soluble in the oil to the extent of 30 to 86 per cent of their volume.

In figure 1 is shown a gas-analysis apparatus for determining the solubility of natural gas in claroline oil or alcohol. It consists of a measuring burette, e, having a capacity of 100 c. c., and an absorption pipette, c. It is provided at the top with a three-way T stopcock, d, so that communication can be made between the burette and outside air, or between the burette and the pipette. Water is used in the burette and mercury in the pipette. To begin an analysis, 35 c. c. of claroline oil or 50 c. c. of alcohol is placed in the pipette c over the

(a) Burrell, G. A., The sampling and examination of mine gases and natural gas, 1913, 116 pp., 2pls., 23 figs.

TESTING NATURAL GASES FOR GASOLINE CONTENT. 33

mercury. A 100-c. c. part of the gas sample is then drawn into the burette, measured, and forced into the pipette c. The pipette c is shaken for about three minutes to thoroughly mix the oil or alcohol and gas. The gas is then transferred to the burette and measured, and the loss in volume is noted. The gas is again passed into the pipette and the shaking operation repeated. Finally the gas is

measured again in the burette. The first and second readings should agree within 0.50 per cent. If they do not, the operation should be repeated until the burette readings become constant.

Below are given tables showing the solubility of natural gas and of methane and ethane in different oils. A 35-c. c. sample of the oil was shaken with 100 c. c. of the gas until absorption of gas by the oil ceased.

34 CONDENSATION OF GASOLINE FROM NATURAL GAS.

It was possible to check the above determinations within 0.50 per cent. Considerable uniformity as regards the solubility of the natural gas in the different oils will be noticed. The claroline oil used had the following characteristics, as determined by I. C. Allen, chemist of the bureau:

The solubility of pure ethane in claroline oil, as determined by the authors, was 68.5 per cent.

USE OF ALCOHOL AS A SOLVENT.

The Bureau of Mines has used ethyl alcohol in much the same manner that claroline oil is used for testing natural gas. Instead of 35 c. c. of the claroline oil, 50 c. c. of ethyl alcohol may be used. The procedure otherwise is exactly the same. The results obtained with alcohol are similar to those with claroline oil.

ORSAT APPARATUS FOR DETERMINATION OF CARBON DIOXIDE AND OXYGEN.

In figure 2 is shown an Orsat apparatus for the determination of carbon dioxide and oxygen in natural gas. The Orsat apparatus is so well known that it needs little description. It is sufficient to say that the burette has a capacity of 100 c.c. The pipette b contains caustic potash solution for the removal of carbon dioxide, and the pipette a contains alkaline pyrogallate solution for the removal of oxygen. The figure (fig. 2) shows the level bottle of the burette, the water jacket, and a three-way stopcock, c. This apparatus may

TESTING NATURAL GASES FOR GASOLINE CONTENT. 35

be used to advantage for examining natural gases to determine whether air has leaked into mains, owing to the reduced pressures that are maintained in pipe lines at some gasoline plants.

SPECIFIC-GRAVITY TESTS.

Natural gas may vary in specific gravity from about 0.56 (air = 1) to as much as 1.65, or from a gas containing methane only as the paraffin hydrocarbon in proportions approaching 99 per cent. or more of the total to an extremely "wet" gas, from which gasoline in quantities up to 4 or 5 gallons per 1,000 cubic feet can be obtained. Specific-gravity tests may be made either by weighing the gas in a small glass vessel or by means of Bunsen's effusion method. The weighing method is the more accurate. The following procedure is adopted by the Bureau of Mines:

A 100-c. c. glass globe, equipped with a stopcock, is exhausted of its contained air, thoroughly dried, and weighed. Natural gas is then introduced and a second weighing made. This weight as compared to that of an equal volume of air at the same temperature gives the specific gravity.

36 CONDENSATION OF GASOLINE FROM NATURAL GAS.

EFFUSION METHOD.

In using the Bunsen effusion method, specific gravities are determined by noting the rate at which a certain volume of the gas passes through a small orifice. The rate at which a like volume of air passes through the orifice is also determined. The specific gravities of the natural gas and air are then in inverse ratio to the squares of the rates of effusion.

Some natural gas contains a large percentage of carbon dioxide. This is a heavy gas, having a specific gravity of 1.53 (air = 1). If it happened to be present in a natural gas mixture and a test were not made for it, an experimenter might be misled into believing that the gas was heavy, because of paraffin hydrocarbons present.

Many samples of natural gas contain large percentages of nitrogen. In an extreme instance the bureau found that a natural gas issuing from the earth in the State of Washington contained 98.5 percet of nitrogen. Proportions of nitrogen as high as 10 per cent in natural gas are not uncommon. The specific gravity of nitrogen is 0.97. If much nitrogen were present an investigator might be misled by the specific-gravity test in that the test would not show the specific gravity of the paraffin hydrocarbons but the specific gravity of the entire mixture, which depends in part upon the content of nitrogen or carbon dioxide, or both.

CONSTRUCTION AND USE OF SCHILLING TYPE OF APPARATUS.

The authors have used the particular type of apparatus known as the Schilling (fig. 3) for the specific-gravity determination. It consists of a glass jar, b, with a metal top - into which fits a brass column having suspended from its base a long graduated tube, a, and at its top a cock, c, and a ground-joint socket, d, into which sets a socket holding a small glass tip, e, closed at the top with a thin piece of platinum, f. In this platinum is a minute hole to permit the passage of gas or air at a very slow rate. All metal parts are nickeled.

TESTING NATURAL GASES FOR GASOLINE CONTENT. 37

The mode of operation is as follows: The glass jar is filled with water to the top graduation of the tube or to a point a little above it. The tube is then withdrawn so that it may be filled with air. The cock on the standard is then closed and the tube replaced in the jar. The cock is then opened and with a stop watch the time is taken that elapses while the water passes from the lowest graduation to the graduation above. The tube is then withdrawn and filled with gas and the procedure repeated. The specific gravity, air being 1, is obtained by dividing the gas time squared by the air time squared. Thus, if A represents the time gas requires to pass through the orifice, and B represents the time air requires to pass through the orifice, the specific gravity of the gas will be represented by (A/B)^2.

USE OF THE PITOT TUBE FOR MEASURING THE OPEN FLOW OF GAS WELLS.

The quantity of natural gas that is discharged from a well is usually measured by means of a Pitot tube. (Fig. 4.) This instrument directly measures the velocity of the gas flow. In its most accurate form it consists essentially of two parts, first a tube pointing upstream for measuring the dynamic pressure and second a means of determining the static pressure. Two pressures are thus obtained. Their difference as rea.d on a U gage gives the velocity or impact pressure of the flowing gas.

As ordinarily used for field work the static pressure of the gas flow is not obtained, the instrument consisting simply of a small tube, which is inserted in the flowing gas (a, fig. 4), just inside the pipe or tubing, a distance of one-fourth to one-third of the pipe's diameter

38 CONDENSATION OF GASOLINE FROM NATURAL GAS.

from the outer edge. The plane of the opening in the tube is held at right angles to the flowing gas. At a convenient distance, varying from 1 to 2 feet, a U-shaped gage (fig. 4) is attached to the other end, which is usually half filled with water. If the gas pressure is high enough to force the water out of the tube, mercury is used, and for pressures that are so great that mercury can not be used, a spring gage is attached. A scale graduated from the center in tenths of 1 inch is placed between the two limbs of the U gage. The distance above and below this center line at which the liquid stands in the gage should be added, the object being to determine the exact distance between the high and the low side of the fluid in inches and tenths.

The top joint of tubing or casing should be free from fittings for a distance of 10 feet below the mouth of the well where the test is made. The test should not be made in a collar or gate or at the mouth of any fitting. The well should be blown off at least three hours prior to making the test, and in some cases as much as 24 hours should be allowed. After the velocity pressure of the gas flowing from the well tubing has been determined in inches of water, inches of mercury, or pounds per square inch as outlined above, the corresponding rate of flow may be ascertained from Table 3, a table prepared by F. H. Oliphant (a) and presented below. The quantities of gas stated in the table are based on a pressure of 14.65 pounds per square inch absolute, and a flowing temperature of 60 F., for a gas having a specific gravity of 0.60 (air = 1). If the specific gravity of the gas is other than 0.6 the flow should be multiplied by